These are fairly large, stout black salamanders with wide silver or white bands. Marbled Salamanders are sexually dimorphic and dichromatic, meaning that males and females are shaped and colored differently. Females are larger and have a duller coloration (i.e., diffuse gray bands), while males are smaller and more vibrantly patterned with a bright silver bands. The ventral coloration is black. Marbled Salamanders are quite stout, even for an Ambystoma. Eggs are laid individually (i.e., not gathered in one mass) and unattached to any surface; instead, they are laid in nests often of around up to 100 eggs per female. They are commonly laid under leaf litter, logs, or other cover on dry ground around ponds, and females attend to eggs until they hatch. Marbled Salamanders have pond-type larvae with tall tail fins and bushy external gills. Hatchlings are dark and nondescript, but older larvae typically gain a distinctive series of light spots along their side. As they age, larvae sometimes develop a yellow or green coloration. Recently metamorphosed Marbled Salamanders are approximately 1.5 inches in length and have a weak pattern of lighter flecks that scarcely resembles that of adults. Adult patterns take some time to develop. Marbled Salamanders reach total lengths of about 3-4 in (7-10 cm).

The broad white/silver bands of this species distinguish it from all other Indiana salamanders and make it unlikely to be confused for any other species.

Ecology and Conservation

Marbled Salamanders are inhabitants of hardwood forests, and they will inhabit upland or lowland areas. They utilize frequently flooded bottomlands in southwestern Indiana, ponds on dry forested ridgetops in south-central Indiana, seasonally wet flatwoods in central and southeastern Indiana, and wet, swampy forests in northeastern Indiana. They have even been found breeding in great numbers in grasslands when forested areas are nearby. Larval Marbled Salamanders will eat aquatic invertebrates as well as larval forms of other amphibians; they will also occasionally turn cannibalistic and consume their own siblings. Adults feed upon a variety of small, terrestrial invertebrates.

Unlike other salamanders of the family Ambystomatidae in Indiana, Marbled Salamanders are autumnal breeders, and most of this activity is concentrated from September to November. Courtship and breeding are conducted on land, and afterwards, females conceal themselves under cover along the edges of dried ponds. Here, they lay their eggs and typically remain with the nest until hatching. Females are commonly found during the breeding season curled around their eggs under logs, leaves, and other types of cover. Once the pond is inundated with water from late autumnal or winter rains, the eggs quickly hatch and larvae overwinter in the ponds. This gives them a good head-start on sympatric spring-breeding amphibians.

Although adults can be more selective than other Ambystoma in their choice of breeding sites, this species is common throughout most of its range in Indiana and adapts relatively well to moderate levels of habitat disturbance and alteration. Currently, there are no major threats to the conservation of this species in Indiana.

Distribution

Marbled Salamanders are widespread throughout the eastern and south-central United States, with populations as far south as Texas and Florida and as far north as Michigan and New Hampshire. Marbled Salamanders are most common in the lowlands of southwestern Indiana and the hills of south-central Indiana but are also present in the upland flatwoods of southeastern Indiana. They range up to Tippecanoe County in western Indiana, and an apparently isolated population is found in the dunes along Lake Michigan. Another isolated population exists in the swamp forests of northeastern Indiana.

Taxonomy

The Marbled Salamander (Ambystoma opacum) has no recognized subspecies. It belongs to the family Ambystomatidae, which is represented in Indiana by eight species (plus the unisexual Ambystoma)--the most of any state!

Literature Cited

Brodman, R. 2003. Amphibians and Reptiles from Twenty-three Counties of Indiana. Proceedings of the Indiana Academy of Science 112:43-54.